Her mom mentioned the call so casually I just assumed she was already up or something. Maybe she was anticipating it. I thought choosing to FaceTime was strange bc a text would suffice if it was just an "omw home" kind of update. But then again I'm not the video calling type anyway.
I thought it was telling that her mother said Savannah promised she'd be home by morning. To me that implies her mother had some level of concern about her being out all night and not returning home. Or that she was going out with people her mother didn't like. Or that she had a patterned behavior of not coming home. Something like that.
Otherwise why promise and reassure somebody you'd definitely do something?